Studies in progress are directed toward uncovering the endocrine and neurocytochemical basis for the development of the hypertension with cardiac, blood vessel and renal morbidity which can be induced by psychosocial stress in mice (Atherosclerosis 14:1971) and rats (Proc. Soc. Exp. Biol. Med. 146, 1974). The responses of the adrenal cortex to acute and chronic stress are being evaluated in normal and isolation reared animals. Principal parameters of adrenal cortical function which are being measured are the thymus involutional response and the alterations in plasma corticoids. Studies using a subhuman primate, Sciamiri sciureus, are also being conducted. Blood pressures are being monitored in members of four separate troops of squirrel monkeys and in animals raised under complete social isolation. Attempts will be made to create psychosocial disruptions with the intent of determining if a sustained hypertension with the accompanying pathology, as seen in rodents, can be induced. Neurocytochemical studies of changes in RNA and protein synthesis are being conducted, using electrophoretic methods, in those areas of rat brains believed to exert control on the endocrine and autonomic responses. Bibliographic references: A model of Psychosocial Hypertension Showing Reversibility and Progression of Cardiovascular Hypertension. Henry, J., P.M. Stephens, and G.A. Santisteban. Circulation Research, Vol. 36, January 1975; The Role of Physiological Stress on Breast Tumor Incidence in Mice. Riley, V., D. Spackman and George Santisteban. Proc. Assoc. Cancer Research. 16:152, 1975.